Pneumatic PDM actuators are extensively employed in guided missile guidance and control systems. They are designed to be driven by analog amplifiers which combine the output of a saw tooth oscillator with analog position command and analog position feedback signals. Utilization of such devices with digital autopilots has required that the position feedback transducer of the actuator be replaced by a digital encoder and that the position command signal be converted from the digital output of the computer to an analog signal. Both of these techniques are very costly and require precision electronic circuitry and angular measurement devices.